This disclosure relates to pressure sensitive adhesive (PSA) articles, particularly those having a thin layer of a silicone-containing PSA between a layer of a conventional PSA and a substrate. Also described is a multilayer coating method in which two or more layers of fluids are coated on a substrate and to articles made using the method.
A fundamental characteristic of a coating process is the number of layers that can be applied per applicator. Single layer coating processes employ applicators that can apply one coating layer at a time, that is, a single coating layer is applied per pass of a web past the applicator. Multilayer coating processes employ applicators that can apply two or more coating layers at a time and are typically premetered processes in that all of the fluid fed to the applicator is applied to the web. Examples of multilayer coating processes include slot, extrusion, slide, and curtain coating processes.
Today, there is much need for high performance coated articles manufactured by coating two or more layers of fluid onto a continuous web. The fluids can be coated using a single layer coating process such that the fluids are coated in series with each layer being dried, cured, etc. before the next one is applied. For reasons such as efficiency and cost, it is usually more desirable to employ multilayer coating processes in which the fluids are coated simultaneously onto the web.
Applicators used in multilayer coating processes can be designed to deliver a wide range of fluids, but this is typically not the case if the fluids are to be coated simultaneously. That is, for a given set of fluids to be coated simultaneously, the particular applicator and process conditions used in a multilayer coating process often dictate how different the fluids can be with respect to a particular property such as surface tension, viscosity, etc. Thus, there is a need for multilayer coating processes that are amenable to coating simultaneously fluids having properties that are very different from each other. There is also a need for multilayer coating processes that employ conventional multilayer coating applicators and are amenable to coating simultaneously fluids having properties that are very different from each other.